B2A part 2, CLUT refactoring

This refactors src/Transform_inl.h to support both A2B and B2A CLUTs.
It should not change A2B's behavior, and B2A is not yet active.  If
anything changes, it ought to just be A2B performance.

Change-Id: I65a2cd43d91bb244e7f6868adb2e7840b20ef0a5
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/391136
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed